A pilot investigation of new superparamagnetic iron oxide (ferumoxytol) as a contrast agent for cardiovascular MRI.

PURPOSE: To evaluate the imaging potential of ferumoxytol, a new superparamagnetic iron oxide colloidal blood pool contrast agent.

MATERIALS AND METHODS: Magnetic resonance (MR) imaging at 1.5 Tesla was performed before and after intravenous injection of ferumoxytol using escalating doses of 0.4, 0.8, 1.2 and 1.6 mg Fe/kg for a total of 4 mg Fe/kg in five subjects imaged with 3D MR Angiography (MRA) of the trifurcation after each dose. In five subjects cardiac cine MRI was performed pre and post 4.0 mg Fe/kg. Image quality was assessed by measuring signal to-noise ratio (SNR) and contrast-to-noise ratio (CNR) in the vascular structures. Pre- and post-dose urine and blood tests as well as EKG/vital sign monitoring were performed to evaluate safety and blood samples were collected for T1 relaxivity measurements.

RESULTS: Cumulative doses of 0, 0.4, 1.2, 2.4 and 4 mg Fe/kg yielded mean SNR in the arteries of 10, 16, 39, 57 and 69 respectively indicating that the higher doses produced higher SNR on 3D vascular images. Similarly aorta SNR on 2D time-of-flight increased from 11.8 without Fe to 15.4 post Fe (p = 0.004) indicating improved image quality on MRA sequences optimized for use without contrast. At 4 mg Fe/kg there was a substantial T1 shortening measured in the blood from 1990 ± 573 ms to 80 ± 42 ms (p < 0.0001), corresponding to the increased SNR. Images of large vascular structures including cardiac chambers, aorta, and pulmonary arteries were excellent post ferumoxytol but images of smaller arteries of the trifurcation were difficult to evaluate due to enhancement of the overlapping veins. No serious adverse events occurred.

CONCLUSION: The new superparamagnetic iron oxide colloid ferumoxytol is a promising blood pool agent especially for cardiac, aorta and pulmonary imaging.